Kawakita Atsushi, Kato Makoto
Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu-cho, Sakyo, Kyoto 606-8501, Japan.
Mol Ecol. 2006 Oct;15(12):3567-81. doi: 10.1111/j.1365-294X.2006.03037.x.
The obligate mutualisms between flowering plants and their seed-parasitic pollinators constitute fascinating examples of interspecific mutualisms, which are often characterized by high levels of species diversity and reciprocal species specificity. The diversification in these mutualisms has been thought to occur through simultaneous speciation of the partners, mediated by tight reciprocal adaptation; however, recent studies cast doubt over this general view. In this study, we examine the diversity and species specificity of Epicephala moths (Gracillariidae) that pollinate Glochidion trees (Phyllanthaceae), using analysis of mitochondrial and nuclear gene sequences. Phylogenetic analysis of Epicephala moths associated with five Glochidion species in Japan and Taiwan reveal six genetically isolated species that are also distinguishable by male genital morphology: (i) two species specific to single host species (G. acuminatum and G. zeylanicum, respectively); (ii) two species that coexist on G. lanceolatum; and (iii) two species that share two, closely-related parapatric hosts (G. obovatum and G. rubrum). Statistical analysis shows that the two species associated with G. lanceolatum are not sister species, indicating the colonization of novel Glochidion host in at least one lineage. Behavioural observations suggest that all six species possess the actively-pollinating habit, thus none of the studied species has become a nonmutualistic 'cheater' that exploits the benefit resulting from pollination by other species. Our results parallel recent findings in ecologically similar associations, namely the fig-fig wasp and yucca-yucca moth mutualisms, and contribute to a more general understanding of the factors that determine ecological and evolutionary outcomes in these mutualisms.
开花植物与其种子寄生传粉者之间的专性互利共生构成了种间互利共生的有趣例子，其通常具有高度的物种多样性和相互的物种特异性。这些互利共生关系的多样化被认为是通过伙伴的同时物种形成而发生的，由紧密的相互适应介导；然而，最近的研究对这一普遍观点提出了质疑。在本研究中，我们使用线粒体和核基因序列分析，研究了为算盘子属树木（大戟科）传粉的Epicephala蛾（细蛾科）的多样性和物种特异性。对与日本和台湾的五种算盘子属物种相关的Epicephala蛾进行系统发育分析，发现了六个基因隔离的物种，这些物种也可通过雄性生殖器形态加以区分：（i）分别专寄生于单一寄主物种（尖叶算盘子和锡兰算盘子）的两个物种；（ii）共存于线叶算盘子上的两个物种；以及（iii）共享两个密切相关的邻域分布寄主（倒卵叶算盘子和毛果算盘子）的两个物种。统计分析表明，与线叶算盘子相关的两个物种不是姊妹物种，这表明至少有一个谱系中出现了新的算盘子属寄主定殖。行为观察表明，所有六个物种都具有主动传粉的习性，因此在所研究的物种中，没有一个成为利用其他物种传粉所带来益处的非互利共生“欺骗者”。我们的结果与最近在生态上类似的共生关系中的发现一致，即榕-榕小蜂和丝兰-丝兰蛾互利共生关系，并有助于更全面地理解决定这些互利共生关系中生态和进化结果的因素。
